Efficient coannihilation process through strong Higgs self-coupling in LKP dark matter annihilation

Transcription

1 Efficient coannihilation process through strong Higgs self-coupling in LKP dark matter annihilation Masato Senami (ICRR, University of Tokyo) in collaboration with Shigeki Matsumoto (KEK) Phys. Lett. B 633 (2006) 671

2 Kaluza-Klein Klein dark matter Non-baryonic cold dark matter is established. Weakly Interacting Massive Particle (WIMP) is excellent candidate Relic abundance Large scale structure WIMP candidate Lightest supersymmetric particle Lightest Kaluza-Klein particle (LKP) in universal extra dimension (UED) models

3 Universal Extra Dimension model Appelquist, Cheng, Dobrescu (2000) Universal means all SM particles propagate in spatial extra dimensions KK tower appear KK number n conservation Minimal Universal Extra Dimension model (MUED) Five space-time dimension The extra dimension is compactified on KK number conservation KK parity conservation LKP is stable MUED model brings only two new parameters. (extra dimension size ) (cut off scale ) c.f. R-parity and LSP candidate of dark matter

4 Masses of KK particles KK particle has degenerate mass in tree level 1-loop corrected mass spectrum (SM massless particles are exactly degenerate) Radiative corrections remove the degeneracy LKP : But, some KK particle are well degenerate with LKP degenerate in mass 1/R=500 GeV, ΛR=20, m h =120 GeV Cheng, Matchev, Schmaltz (2002) 1~5%

5 Coannihilation Some KK particles are degenerate with LKP in mass. δ=o(1)% : MUED model Relic abundance Coannihilation should be considered. Coannihilation changes relic abundance of DM. < abundance is increased > abundance is decreased c.f. SUSY models: coannihilation effects decrease the abundance

6 Relic abundance Relic abundance Including coannihilation In their result, 1/R = GeV is reported for MUED m h =120 GeV was assumed. Servant, Tait (2003), Kakizaki, Matsumoto, Sato, Senami (2005) Kong, Matchev (2005), Burnell, Kribs (2005) Kong, Matchev (2005) 1/R (GeV) But, the relic abundance is dependent on Higgs mass

7 KK Higgs particle KK Higgs mass Charged LKP % larger larger, smaller (can be negative) % 1% For m h ~200 GeV, mass difference between LKP and is very small In summary Larger m h larger enhance annihilation of

8 Relic abundance of LKP GeV 170GeV 200GeV 220GeV 0.1 m h large 230GeV /R (GeV) Allowed region : for

9 Conclusion Charged LKP region (Excluded) Relic abundance of LKP depend heavily on SM Higgs mass Large m h large Higgs self coupling large annihilation cross section of KK Higgs /R (GeV)

10 Electroweak Precision Measurement

11 Annihilation after decoupling g : degree of freedom of KK particles total LKP 10 KK lepton KK Higgs Difference : KK Higgs total LKP KK lepton KK Higgs

12 KK Graviton 1/R < 800GeV KK graviton may be LKP i.e. DM is SuperWIMP CMB and diffuse gamma exclude KK graviton DM Feng, Rajaraman, Takayama, PRL91, PRD68 1>R 800GeV MUED is consistent with DM relic abundance only if m h > 220GeV. KK graviton become heavy KK Graviton is LKP Higher space-time dimension > MUED KK particle in MUED in five dimension space-time KK graviton in higher dimensional space-time /R (GeV)

13 Comparison Our result is different from that of Kong and Matchev. Our result : 1/R = GeV solve Boltzmann equation numerically Kong and Matchev s result : 1/R = GeV use approximation formula In UED model, we must solve the Boltzmann equation numerically. Senami and Matsumoto, in preparation

14 does not couple with SM particle at tree level Second KK s-channels We find Since DM is non-relativistic, the incident energy of two LKPs is almost degenerate with the mass of second KK modes In particular, s-channel LKP annihilation process mediated by competes with tree level diagrams because of the resonance One of the resonant diagrams We calculate these type of diagrams

15 h = 120 GeV (1) m 200 GeV (2) = 250 GeV (3) = 400 GeV (4) = h = 120 GeV (1) m 200 GeV (2) = 250 GeV (3) = 400 GeV (4) = Cross section 3.0 Cross Section (10 26 cm 3 sec 1 ) (3) For small mass differenceδ, incident energy matches the pole and averaged cross section is enhanced. m is LKP mass For smaller δ, the averaged cross section is maximum at later time and has larger maximum value. Relic density is reduced compared to the tree result by this enhancement of the cross section (4) x = m=t Y=Y tree (1) Tree (2) (4) (1) (2) (3) x = m=t

16 Dark matter relic abundance General picture At T ~ m (x~1), dark matter particle is in thermal equilibrium. After annihilation rate dropped below the Hubble parameter, dark matter can not annihilate and the density per comoving volume is fixed. Co-moving number density Relic abundance Decoupling thermal equilibrium Increasing x = m / T (time) Large cross section small relic abundance of dark matter

17 Tree level mass relation

18 Weak mixing angles Cheng, Matchev, Schmaltz